News Archive
Issue 7 July 2008
Protect your pump from gremlins…
Progressing cavity pumps are often selected for arduous conditions
due to their solids and abrasion handling abilities; however, these
pumps, along with other positive displacement pumps and equipment,
still require protection from, typically:-
- Rags and bags
- Tin cans and plastic bottles
- Oversized solids that would jam within the pumping chamber
You can protect your pump from these objects with screens or grinders,
the latter being available in pipeline or channel configuration
to suit your plant layout.
Macerators are also available, but their function is generally
for fluid conditioning rather than plant protection. A typical macerator
application would be sludge feed to a digester, the sludge / solids
being reduced in size, therefore increasing their surface area to
aid the biological process. Solids reduction size is determined
by the hole size in the fixed shear plate and the rotational speed
of the cutters.
The hole size in the macerator acts as a screen, hence a macerator
can be used for equipment protection, but if more than occasional
quantities of foreign bodies are present in the system you should
consider using a grinder.
Grinder design generally consists of two counter rotating shafts
fitted with intermeshing cutters and spacers. Rags, bags and tins
are simply cut into small particles that will then pass safely through
your downstream equipment.
Grinders are sized against your system’s flow requirements,
the size of grinder or surface area of the cutting screen being
such that it does not create unnecessary back pressure or blockage
within your system. The speed of the grinder is set for maximum
cutting efficiency and has no effect on the flow capacity of your
grinder or system.
Another grinder selection consideration should be maintenance.
Costs and downtime can be significantly reduced by selecting a design
that allows easy withdrawal and replacement of the cutting cartridge.
If using a channel grinder situated within a manhole or confined
space, guide rails and lifting chain are worthwhile additions that
you should also consider with your initial purchase.
For more information on grinders please do not hesitate to call
our technical office in Southampton and we would be more than pleased
to discuss this technology with you. We’re more than just
a sales office, so you don’t need to be looking to purchase
to call! Tel (00) 023 8076 0000.
Centrifugal submersible pump out performed by R&M 500 PC Grinder
Pump…
Domestic, campground and recreation to light industrial waste water
and sewage applications have been serviced by small submersible
pump tanks and stations reliably for decades. However, for sites
with high elevation and relatively low flow requirements these centrifugal
pumps have been operating near to their closed valve pressure limitation.
The result for many end users of these applications is poor flow
control, occasional backflow and or long pump run times, premature
pump wear and even breakdown.
The Robbins & Myers Moyno 500 Grinder pump, time-served in commercial
shipping septic and bilge applications, provides reliable steady
flow up to 3 bar pressure and is rapidly becoming adopted for reliable
high head waste water and sewage applications; typically, for domestic
and camping ground type applications. They’re even permitting
new facility layouts, not feasible with centrifugal submersible
pumps, due to their limited pressure capability.
For further information or pump selection please contact our technical
office, email sales@robn.com
or tel. (00) 023 8076 0000.
Very best regards
David Johnson
Business Development Manager